Dechannelling Cylinder of Dislocations

A particle channelled in a crystal may be dechannelled when passing near a dislocation. This effect is simulated by an opaque cylinder dechannelling any particle hitting it. This cylinder is coaxial to the dislocation and has a diameter\documentclass{article}\pagestyle{empty}\begin{document}$$ \overline \lambda = \left({\frac{{b\,d\,a\,E}}{{\alpha Z_1 Z_2 e^2}}} \right)^{1/2}.$$\end{document}E is the energy of the particle (charge Z 1 e ), b the Burgers vector, d the interatomic distance along the considered channel in the crystal Z 2 , a the screening radius, and α a number equal to 12.5 and 4.5 for screw or edge dislocations, respectively.